A video on demand service permits a viewer to order a movie or other video program material for immediate viewing. In a typical broadcast satellite or cable television (CATV) system, the viewer is presented with a library of video choices. The VOD program material, such as for example movies, are referred to herein as assets, programs or content. The viewer may be able to search for desired content by sorting the library according to actor, title, genre or other criteria before making a selection. In general, assets, programs and content include audio files, images and/or text as well as video.
In a VOD system, a portion of the CATV spectrum may be dedicated (on a per use basis) to transmit the requested video to the subscriber. Instead of using a portion of the CATV spectrum, another transport path such as an IP path may be used. The practice of assigning a portion of the CATV spectrum on a temporary basis is known as narrowcasting. Likewise, an IP path would be implemented using singlecast IP addressing. Since the assigned video channel is dedicated to one viewer, VCR-like commands are possible. That is, for example, the purchased video may be paused, fast-forwarded, rewound or played in slow motion. Various vendors, known as VOD suppliers, provide systems and software that enable CATV operators to offer a VOD service to their subscribers.
In a typical VOD system, an application software component (known as the VOD client) resides in the CATV set-top box (STB) at the viewer's home. A typical VOD system further includes a VOD server, which is a memory intensive system that stores VOD content at the headend and generates the VOD video stream for each subscriber. The video inventory in the VOD server may contain thousands of titles. The VOD server further generates one VOD video stream for each active VOD viewer. There may be thousands of simultaneous active VOD viewers. A VOD pump streams the VOD content from the VOD server. In addition to a VOD pump, a typical VOD system includes a VOD asset management system, a resource management system, a VOD business management system and a conditional access system.
The VOD asset management system generates lists of movies or other content that are available for VOD purchase. The VOD client communicates requests to the VOD management system at the CATV headend and the resource management system sets up the VOD pump to transmit the movie to the viewer. The resource manager also provides tuning information to the set-top via the appropriate VOD server element. Also, for billing purposes, the VOD business management system records the event of a video purchase and communicates the purchase event to a billing system through which the viewer pays for the video purchase.
The system implementing VOD often provides the capability to limit content access to authorized subscribers only, as the content is delivered as part of the service are generally considered valuable intellectual properties by their owners. In cable and satellite television, such capability is known as conditional access. Conditional access requires a trustworthy mechanism for classifying subscribers into different classes, and an enforcement mechanism for denying access to unauthorized subscribers. Encryption is typically the mechanism used to deny unauthorized access to content (as opposed to denying access to the carrier signal).
To use conditional access with VOD systems, the content may be pre-encrypted before it is stored on the video server. Pre-encryption requires preprocessing content as it is transferred from the content owner to the cable operator. This may require an additional memory cache requirement for processing and transporting the content.
In addition, the management and distribution of encryption keys is also required as part of a VOD session, possibly requiring the use of an Encryption Renewal System. Depending on the particular implementation, there may also be the need for additional processing of the outgoing pre-encrypted streams. Alternatively, if real-time encryption during an on-demand session is employed using industry standard architectures, an enhanced resource manager is needed to coordinate the operation of the VOD servers, encryptors and the set top boxes. In particular, the resource manager interfaces with the VOD servers for session signaling protocol conversion with the set-top box, including session setup and tear down. The resource manager still performs such functions as determining the bandwidth required for given session and allocating the necessary frequency spectrum as required for the session. The resource manager also communicates the assigned VOD channel to the VOD client in the set-top box. In such manner, the set-top-box tuner is able to tune to the channel containing the video that was ordered by the subscriber. In addition, the resource manager must coordinate encryption resources for delivering the VOD stream, which is not necessary in existing pre-encryption system.
Accordingly, in implementing a real-time encryption VOD system, the communication between the VOD servers, distribution networks, encryptors and the set top boxes requires a relatively complex set of protocols to implement. The protocols employed between the VOD servers, distribution networks, and set-top boxes has largely been developed and deployed. On the other hand, the protocols used between the resource manager, VOD server and encryptors present a number of problems, because the protocols will generally need to be different for VOD servers supplied by different vendors. As a result, the VOD operator may be forced to delay introduction of certain features and implementations until they are supported by the incumbent VOD vendor or the operator may have to wait for a specific implementation to be supported by the VOD vendor.